The present invention relates to location-force target path creators, and more particularly to a location-force target path creator adapted to create a smooth form of a time function with a plurality of target values among in location, position, force or moment that are given for a force control system.
Where realizing a force control system for robots or machine tools, the process as shown in FIG. 11 is usually carried out. That is, at step 1 (hereinafter denoted as S1 in the figure), the instructions from an operator is interpreted as data as to location, force, position, moment, etc. Then, at step 2, a working region, a maximum speed, etc. are determined depending upon the data, etc. obtained at step 1 for calculating in what way a robot or the like is operated for its feasibility, thereby planning the path thereof. At step 3, the coefficient data, etc. for a target value function is calculated to establish a target value function, to thereafter calculate and output target paths in real time. At step 4 and the subsequent steps, feedback control is made based on the calculated target paths. At step 5, the target path data is applied to a mechanism section, such as a motor and a driver, of which force or torque is to be controlled so that the amount thereof is fed back at step 6. In the motion control structure as set forth above, the processes of step 1 through step 3 are for planning wherein target values in location and force are created.
However, although conventionally there have been often studies on force control shown in step 4 and the subsequent steps, it is the practical situation that studies were rarely made for the planning section. Meanwhile, as regard to studies on force control, there is often a case that the reference input to a force control system is limited to step inputting or it is handled as ambiguous one without definition. This seems to be a factor that the effectiveness cannot be appreciated to a full extent, even where a robust force control system can be applied to an actual system. On the other hand, where the location and position only are designed for target paths, they are, though effective for actuation such as gripping and releasing in three dimensions, difficult to apply to such a control operation that involves force of assembling, grinding and debarring, etc. If a force reference input is used for step input as above, a kind of impact occurs at non-continuous portions with a fear of causing residual vibrations, deformations, breakage, etc.
The present invention has been made in view of the conventionally-encountered problems, and it is the object of the present invention to provide a location-force target path creator which is capable of creating a smooth form of a time function with a plurality of target values among in location, position, force and moment given to a force control system.